Vacuum electric switch



April 11, 1961 JENNINGS 2,979,587

VACUUM ELECTRIC SWITCH Filed Oct. 28, 1958 \muu INVENTOR.

Jo I'M/1577' JiIV/W/VGJ United States Patent Ofiice Patented Apr. 11, 1961 VACUUM ELECTRIC SWITCH Jo Emmett Jennings, San Jose, Calif., assignor to Jenmugs Radio Manufacturing Corporation, San Jose, Calif a corporation of California Filed Oct. 28, 1958, Ser. No. 770,157

12 Claims. c1, 200-144 My invention relates to a vacuum electric switch in which relatively movable or moving parts are electrically bonded together or connected so that its current carrying capacity is very substantially increased.

An important object of my invention is to provide, in a vacuum switch in which the base or mounting flange is integrally connected to the actuator stem, an additional bonding connection which can be readily separated at need, but which is substantially the equal of an integral union when made.

Still another object of my invention is the provision of means in a vacuum switch having an actuator shaft, of a dielectric bearing for the shaft, so that passage of are forming current between the relatively moving and movable shaft and bearing is avoided.

Another object is the provision in a vacuum switch of means for presetting adjustment of the spring tension which regulates operation of the switch; and which presetting is essential for assembly-line mounting of the switches.

Another object of my invention is the provision of a vacuum switch of the general character described in which the generally tubular construction employed is more compact, safer and neater in appearance than is possible in conventional electrical bonding practice.

Other objects of the invention together with the foregoing will be set forth in the following description of .thepreferred embodiment of my invention which is illustrated. in the accompanying drawing. It is to be understood that I do not limit myself to the showing made by the said'description and drawing, as I may adopt variations of my preferred form within the scope of my invention as set forth in the claims.

The figure of the drawing is a partial half sectional view of a vacuum switch embodying my invention, the plane of section lying in the long axis of the implement.

In vacuum switches which employ a bellows to effect a perfect seal between the main body of the envelope and the relatively movable actuator stem, the bellows permits the passage of a limited amount of current from the switch contacts tothe base constituting the mounting flange of the implement. In power work, such as 60 cycle A'.C. or in DC, and in low frequencies where the skin effect is negligible, it is necessary to carry varying amounts of electrical current through the actuator stem.

Heretofore this has been accomplished, but with recognized imperfections, by the use of a laminated flexible copper strip in fixed connection with the actuator stem adjacent center of the strip, and having the ends of the strip curved around and fixed to opposite sides of the mounting flange. This is effective although cumbersome; and current capabilities are increased many times by the use of this strip conductor, bonding the actuator stem to the mounting flange.

Broadly it is the purpose of my present invention to provide a bonding structure safer and more eflicient electrically and mechanically than any I have previously known, readily capable of presetting adjustment for assembly-line mounting, compact and attractive in design. And above all, providing a clampedly secure as well as an integral conductive path from actuator shaft to mounting flange.

In detail my vacuum switch comprises a glass shell 2 closed at its upper end with the copper cap 3, connected hermetically to the glass shell by the conventional seal 4. The cap is provided with the central cylindrical extension or lug 6, by which the switch is connected into circuit by a suitable clamp or bracket.

The lug of the cap is filled with a copper plug 7 brazed in place; and the inner end of the plug serves as a mounting for both the shield 8 and the tungsten switch point 9, which terminates well within the shield.

0n the opposite end of the glass shell, the copper terminal cap 12 provides a seat for the annular base 13 and the bellows 14, all integrally brazed together and hermetically sealing the adjacent end of the switch envelope formed by the shell 2 and two caps. The terminal cap 12 is formed with the inwardly extending concentric L-shaped flange 16 in which the annular bellows base 13 is seated from the outside of the envelope, having previously been brazed to the lower flange 17 of the bellows assembly. The inner end of the bellows 14 is fully closed by the end 18, heavily overlaid and reinforced by the bellows cap 21 Both end and cap are brazed together and to the stainless steel actuator stem 22, terminating at its inner end in a tungsten contact point 23, in axial alignment with the fixed contact point 9.

I The annular base 13 is provided near its inner periphery with a short cylindrical concentric flange 24, having its lower outer edge rabbeted as shown. Seated within the flange 24 and against the inner edge of the base 13 is the slide bearing 26, extending well into the bellows, and in which the actuator stem 22 is slidably journaled.

Surrounding the flange 24 on the outside is the strengthening and stiffening annular steel mounting plate 27, to which the terminal cap 12 and the bellows plate 13 are brazed along their outer flat surfaces 28. Underlying the mounting plate is a second plate 29, of copper because of its high conductivity. 'The copper plate is substantially coextensive with the steel mounting plate and the two may be combined into a unitary mounting plate if necessary strength and conductive qualities are provided.

On its inner periphery the copper plate is formed with an offset flange 31, so shaped as to complement the rabbeted edgeof the flange 24 and overlie the peripheral edge of the lower end of the bearing 26, thus clamping pheric pressure on the bellows so that the switch is operative as'shown, in normally open position and with predetermined pressure values. In connection therewith, the actuator stem 22 is fixedly connected electrically with the copper conductive plate 29, so that current through the switch may flow not only through the bellows cap 21, bellows 14, terminal cap 12 and plate 13 in an integrated conductive path including mounting plate 27, but also through a clampedly joined conductive path through the stem 22 and flange nut 36, tightly threaded on the end of the stem and brazed to the lower end of the bellows 37. The upper end of the bellows is fixedly connected to the copper component of the mounting plate by the clamp ring 38 secured by screws 39.

The coiled compression spring 32 impinging against the lower end of the slide bearing 26 bearsagainst the upper face of the nut 36, the turning of which, with the clamp ring 38 loosened, adjusts the expansion pressure exerted by the spring to hold the stern and switch point 23 in normally open position when the closing pressure is relaxed.

A lock nut 41 effectively fixes the position of the nut 36 on the stern, leaving a short threaded end for connection into the copper tip 42 of the ceramic actuator rod 43, motorized by conventional or other means.

In some usage it is desirable to surround the external bellows and operative connections with a protective dielectric enclosure. This is readily accomplished by a ceramic shell 46, metallized on one edge to carry the brazed-on mounting ring 47, caught under the heads of the bolts 48 which bind the two parts of the mounting plate together. This ring is provided with openings 49 spaced closely therearound, for ventilation and also for xposure of the screws 39.

The other or lower end of the shell 46 is also metallized to carry the guard ring 51 which closely surrounds the ceramic actuator rod 43.

It should be noted that since the stem 22 has a sliding contact with the bearing 26, there could be occasions when a difference in potential between stem and bearing would cause arcing and welding of adjacent surfaces. To prevent this, I prefer to make the bearing 26 of Teflon or other dielectric synthetic so as to insulate the metal stem throughout the area of its contact with its supporting hearing. If the danger of arcing does not exist, metal may be used for hearing 26.

From the above it should be clear that current may pass through the switch from the stem 22 to the mounting plate via the bellows 14 and integrally connected parts; and that additional current passes from the stem to the mounting plate via the bellows 37 and parts both integrally and clampedly connected, so that together the total current which my switch is capable of handling is greatly increased without overheating. It is also clear that in the making of my switches, accurate adjustment of the balancing spring 32 is readily accomplished in the assembly line.

The short external bellows gives low inductance and high conductivity at a minimum space requirement; and since the bellows is not subjected to the high temperature of vacuum processing, less convolutions are used and longer life is assured.

I claim:

1. A vacuum switch comprising a generally cylindrical dielectric shell, an upper and a lower metal end cap closing the ends of the shell to form a vacuumized envelope, a metal actuator stem slidably journaled in the lower end cap and extending outside of the envelope, a metal bellows inside the envelope interposed between said lower end cap and the actuator stem to hermetically seal the envelope and electrically connect the stem and lower end capfa coil spring surrounding the stem and interposed between the stem and thelower endcap, a metal bellows outside the envelope and surrounding the can an ataway e erat a ama t lower end cap, and means for varying the tension of the spring. a a

2. A combination in accordance with claim 1 in which the actuator stem is journaled in a dielectric sleeve insulating it from the metal portion of the lower end cap.

3. A vacuum switch comprising a generally cylindrical dielectric shell, an upper and a lower metal end cap closing the ends of the shell to form a vacuumized envelope, a metal actuator stem slidably journaled in the lower end cap and extending outside of the envelope, a metal bellows inside the envelope interposed between said lower end cap and the actuator stem to hermetically seal the envelope and electrically connect the stem and lower end cap, a metal flange-nut fixedly and adjustably mounted outside the envelope on the actuator stem, a coil spring surrounding the stem and interposed between the flange-nut and the lower end cap, and a metal bellows outside the envelope and surrounding the coilspring and electrically connected to both flange-nut and lower -end cap.

4. A vacuum switch comprising a generally cylindrical dielectric shell, an upper and a lower metal end cap closing the ends of the shell to form a vacuumized envelope, a metal actuator stern slidably journaled in the lower end cap and extending outside of the envelope, a metal mounting plate on which said lower end cap is secured, a' metal bellows inside the envelope interposed between said lower end cap and the actuator stem to hermetically seal the envelope and electrically connect the stem and mounting plate, a metal flange-nut fixedly and adjustably mounted outside the envelope on the actuator stem, a coil spring surrounding the stem and interposed between the flange-nut and the mounting plate, and a metal bellows outside the envelope and surrounding the coil spring and electrically connected to both flange-nut and mounting plate. a

5. A combination in accordance with claim 4 in which the metalmounting plate is formed of two layers, one having rigidity and strength and the other a high degree of electrical and thermal conductivity.

6. A combination in accordance'with claim 4 in which a dielectric shell surrounds the external bellows, andmeans are provided for mounting the dielectric shell on the mounting plate.

7. A combination in accordance with claim 4 in which the actuator stem is journaled in a dielectric sleeve insulating it from the metal portion of the lower end cap.

8. In a vacuum switch, a generally cylindrical dielectri c shell, an upper metal end cap closing the upper end of the shell, a contact point fixedly mounted in the upper end cap, a lower metal end cap closing the lower end of the shell and having an annular flanged seat surrounding'a central opening therein, a closed end bellows" having itsopen end brazed to the end cap around the opening to form with the shell and end caps a vacuumized envelope, a bearing sleeve disposed in the flanged seat, a conductive mounting plate underlying and secured to the lower end cap and a marginal zone of the bearing sleeve, a conductive stem slidable in the bearing sleeve and brazed to the bellows end and extending therethrough to provide within the envelope a contact point in alignment with the fixed contact point and an extended end outside the envelope, a flange adjustably fixed on the extended end of, the stem, a spring interposed between the flange and end cap, and an external metal bellows surrounding the spririg and fixed atone end to the flange and to the mounting plate at the other end.

9. A switch in' accordance with claim 8 in which a dielectric shell surrounds the bellows and spring, and means are provided for securing the surrounding shell on the mounting plate. r

10. A 'switch in accordance with claim 8 in which'the flange is a nut threaded'on the eudof the stem,' the adiaf' an fihi sX inal b l w? s. brazi l 1?? ,3?!

and a clamp ring secures the other end of the bellows to the mounting plate.

11. A switch in accordance with claim 10 in which the bearing sleeve is of dielectric material.

12. In a vacuum switch, a conductive mounting plate, a movable conductive stem extending into the atmosphere beyond said plate, a flange tightly united to said stem, a compression spring surrounding said stern and interposed between said plate and said flange, a bellows surrounding said spring and integrally united at one end to said flange and abutting said plate at its opposite end, and a releasable clamp ring pressing said opposite end tightly against said plate.

References Cited in the file of this patent UNITED STATES PATENTS Rankin Apr. 25, 1933 Cunningham Sept. 27, 1955 Schwager June 10, 1958 Reece Apr. 18, 1959 FOREIGN PATENTS Great Britain Jan. 15, 1931 Germany Nov. 3, 1932 Great Britain Dec. 18, 1957 

